Upgrade newrelic agent to the latest version
Keep comments in capa XML from causing failures

Comments (and processing instructions!) are handled oddly in lxml.
This change will keep them from causing failures.  They will be omitted
from the HTML generated, which is fine, since they aren't needed there.
A test that our XML-comments fix works.
Move mitxmako initialization to a startup module, called by lms.startup and cms.startup for both management commands and when run via wsgi

[DEVPAIN-7]
Check extension rather than mimetype
Merge pull request #819 from edx/jkarni/hotfix/gzip-mimetype

Check extension rather than mimetype
Merge pull request #816 from edx/hotfix/xml-parsing

Hotfix/xml parsing
Reset 'correctness' visual indicator of a problem on new input

Affects:
Choicegroups, option inputs, textline, and formula equation inputs
Merge pull request #794 from cpennington/upgrade-newrelic

Upgrade newrelic agent to the latest version
Merge pull request #811 from cpennington/initialize-mitxmako-at-startup

Move mitxmako initialization to a startup module
Updated acceptance tests to match new behavior in video captions.
using mocks to make test_err_handling.py faster
remove vestigal references to fake_smtp_server
restructure calc
specify preview import statements to reflect new package structure
change calcfunctions -> functions
bump version number on calc
Merge pull request #843 from edx/adam/calc-refactor

Adam/calc refactor
Merge pull request #841 from edx/jbau/bulk-email-faster-tests

Jbau/bulk email faster tests
Acceptance tests for visual correctness reset feature